Jupyter Notebook: Python Advanced (2023-04-24 - 2023-04-26)

Iterator Protocol

for i in range(3):
    print(i)

0
1
2

for i in [0,1,2]:
    print(i)

0
1
2

drei_millionen_ints = list(range(3_000_000))

type(drei_millionen_ints)

list

r = range(3)

print(type(r))

<class 'range'>

it = iter(r)

print(type(it))

<class 'range_iterator'>

next(it)

0

next(it)

1

next(it)

2

try:
    next(it)
except StopIteration:
    pass

for i in range(3):
    print(i)

0
1
2

numbers = range(10)

def odd_numbers(iterable):
    for number in iterable:
        if number % 2 != 0:
            print('next element')
            yield number

for i in odd_numbers(numbers):
    print(i)

next element
1
next element
3
next element
5
next element
7
next element
9

def odd_numbers_func(l):
    ret_nums = []
    for number in l:
        if number % 2 != 0:
            ret_nums.append(number)
    print('returning result')
    return ret_nums

for i in odd_numbers_func(numbers):
    print(i)

returning result
1
3
5
7
9

Dynamic Features

a = 42

globals()['a']

42

globals()['numbers']

range(0, 10)

code = '''
eine_variable = 7
'''

context = {}

exec(code, context)

context['eine_variable']

7

class Foo:
    def __init__(self, bar, blech):
        self.bar = bar
        self.blech = blech

f = Foo('Joerg', 'Faschingbauer')

f.__dict__

{'bar': 'Joerg', 'blech': 'Faschingbauer'}

print(type(odd_numbers))

<class 'function'>

print(type(a))

<class 'int'>

odd_numbers.__name__

'odd_numbers'

blah = odd_numbers

blah

<function __main__.odd_numbers(iterable)>

blah.__name__

'odd_numbers'

Variables

a = 42

print(type(a))

<class 'int'>

a = 1.234

type(a)

float

a = [1,2,'drei']

type(a)

list

a = odd_numbers

type(a)

function

t = (1,2)

type(t)

tuple

x, y = t

x

1

y

2

x, y = 1, 2

x, y = (1, 2)

x, y = 1, 2

tmp = x

x = y

y = tmp

x

2

y

1

x, y = 1, 2

x, y = y, x

x

2

y

1

a = 42

b = a

hex(id(a))

'0x7f32ccc4c610'

hex(id(b))

'0x7f32ccc4c610'

Datatypes

i = 42

i = 2**64-1

bin(i)

'0b1111111111111111111111111111111111111111111111111111111111111111'

i += 1

i

18446744073709551616

bin(i)

'0b10000000000000000000000000000000000000000000000000000000000000000'

10**6

1000000

10**10

10000000000

10**100

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

10**1000

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

3/2

1.5

is vs. ==

l1 = [1,2,3]

l2 = [3,4,5]

id(l1)

139855258515840

id(l2)

139856078033344

l1 is l2

False

l1 == l2

False

l3 = [1,2,3]

id(l3)

139856078226432

l1 is l3

False

l1 == l3

True

l1.append(4)

l1

[1, 2, 3, 4]

l3

[1, 2, 3]

i1 = 42

i2 = i1

id(i1)

139856160540176

id(i2)

139856160540176

i1 is i2

True

i1 == i2

True

i1 = 42

i2 = 42

i1 is i2

True

i3 = 10**1000

i4 = 10**1000

i3 is i4

False

b = False

if b is False:
    print('yay')

yay

if b == False:
    print('yay')

yay

if b:
    print('nope')

l3

[1, 2, 3]

if l3:
    print('yay')

yay

if []:
    print('yay')

s = 'abc'

if s:
    print('yay')

yay

if '':
    print('yay')

Datatype Conversions

s = 'abc'

print(type(s))

<class 'str'>

i = 42

s = str(i)

s

'42'

s == i

False

str()

''

int()

0

i = int('42')

i

42

int('42', 16)

66

int('0101010101010', 2)

2730

print(type(l1))

<class 'list'>

list()

[]

list('abc')

['a', 'b', 'c']

for c in 'abc':
    print(c)

a
b
c

l = []
for c in 'abc':
    l.append(c)

l

['a', 'b', 'c']

list(range(3))

[0, 1, 2]

type(l)

list

type(42)

int

print(int)

<class 'int'>

print(type(int))

<class 'type'>

int = 666

try:
    int('42')
except TypeError as e:
    print(e, type(e))

'int' object is not callable <class 'TypeError'>

import os
os.listdir('/home/jfasch')

['.bash_logout',
 '.bash_profile',
 '.cache',
 '.config',
 '.local',
 'Desktop',
 'Downloads',
 'Templates',
 'Public',
 'Documents',
 'Music',
 'Pictures',
 'Videos',
 'old-home',
 'Homebrain',
 '.thunderbird',
 '.mozilla',
 'work',
 'venv',
 '.emacs.d',
 '.bashrc~',
 '.emacs',
 '.gnupg',
 'tmp',
 '.wget-hsts',
 '.cups',
 '.gitconfig',
 '.pki',
 '.var',
 '.zoom',
 '.mplayer',
 '.ipython',
 '.jupyter',
 'hello.~1~',
 'x-tools',
 'cross',
 'build',
 '.dia',
 '.bashrc.~1~',
 '.bashrc.~2~',
 '.bashrc',
 'raspi-home',
 'daham',
 'C++-Training-2023-03-20',
 '.ssh',
 '#*message*-20230403-222915#',
 'blink-home',
 'can.log',
 '.bash_history',
 '.python_history',
 '.lesshst']

import os
os.listdir = lambda d: []

os.listdir('/home/jfasch')

[]

os.listdir = None

try:
    os.listdir('/home/jfasch')
except TypeError as e:
    print(e, type(e))

'NoneType' object is not callable <class 'TypeError'>

Compound DataTypes

List, Tuple

l = [1,2,3]

l.append(4)

l

[1, 2, 3, 4]

l.extend([5,6,7])

l

[1, 2, 3, 4, 5, 6, 7]

l.extend('abc')
l

[1, 2, 3, 4, 5, 6, 7, 'a', 'b', 'c']

try:
    l.extend(666)
except TypeError as e:
    print(e, type(e))

'int' object is not iterable <class 'TypeError'>

l.append([8,9,10])
l

[1, 2, 3, 4, 5, 6, 7, 'a', 'b', 'c', [8, 9, 10]]

l[0]

1

l[1]

2

l1 = [1,2,3]

id(l1)

139855258795072

l2 = [4,5,6]

l1 + l2

[1, 2, 3, 4, 5, 6]

id(l1)

139855258795072

l1 += l2

l1

[1, 2, 3, 4, 5, 6]

id(l1)     # <--- mutable

139855258795072

t = (1,2,3)
print(type(t))

<class 'tuple'>

t

(1, 2, 3)

t[0]

1

t[1]

2

try:
    t.append(4)
except AttributeError as e:
    print(e, type(e))

'tuple' object has no attribute 'append' <class 'AttributeError'>

id(t)

139855260513728

t += (4,5,6)

id(t)

139856085569920

Dictionary

d = {
    'one': 1,
    'two': 2,
}

d['one']

1

'one' in d

True

'four' in d

False

'four' not in d

True

d['four'] = 'vier'

d

{'one': 1, 'two': 2, 'four': 'vier'}

del d['four']

'four' in d

False

d['four'] = 'vier'

pop

elem = d['four']
del d['four']
elem

'vier'

d['four'] = 'vier'

elem = d.pop('four')
elem

'vier'

try:
    d.pop('four')
except Exception as e:
    print(e, type(e))

'four' <class 'KeyError'>

get

try:
    elem = d['four']
except KeyError:
    elem = None
if elem is None:
    print('nix')
else:
    print('yay')

nix

elem = d.get('four')
if elem is None:
    print('nix')
else:
    print('yay')

nix

Doppelt gemoppelt:

if 'four' in d:     # <--- constant time
    elem = d['four']
else:
    elem = 4
print(elem)

4

Einfach gemoppelt:

elem = d.get('four', 4)
print(elem)

4

keys()? in?

if 'four' in d.keys():    # <--- sequential search!
    elem = d['four']
else:
    elem = 4
print(elem)

4

keys = d.keys()
type(keys)

dict_keys

Wenn 'four' nicht in d, dann trag 4 ein (und gib 4 zurueck). Wenn doch drin, gib dessen Wert zurueck.

if 'four' not in d:
    d['four'] = 4
    value = 4
else:
    value = d['four']
print(value)

4

del d['four']

setdefault

Exakt das gleiche:

value = d.setdefault('four', 4)
print(value)

4

Dictionary constructor

d = {
    'one': 1,
    'two': 2,
    'three': 3,
}

d

{'one': 1, 'two': 2, 'three': 3}

d = dict([('one', 1), ('two', 2), ('three', 3)])

d

{'one': 1, 'two': 2, 'three': 3}

Dictionary iteration

Key iteration, implizit

for elem in d:
    print(elem)

one
two
three

Key iteration, explizit

for k in d.keys():
    print(k)

one
two
three

Value iteration

for v in d.values():
    print(v)

1
2
3

Paarweise iteration (keys, values)

for elem in d.items():
    print(elem)

('one', 1)
('two', 2)
('three', 3)

Tuple unpacking

x, y = (1,2)

x

1

y

2

for elem in d.items():
    k = elem[0]
    v = elem[1]
    print(f'key: {k}, value: {v}')

key: one, value: 1
key: two, value: 2
key: three, value: 3

for k, v in d.items():
    print(f'key: {k}, value: {v}')

key: one, value: 1
key: two, value: 2
key: three, value: 3

Set

s = {1,2,3}

s = set()

s = set('abc')
s

{'a', 'b', 'c'}

'a' in s

True

s.add('d')

'd' in s

True

s.remove('a')

'a' in s

False

s = frozenset('abc')

try:
    s.add('d')
except Exception as e:
    print(e, type(e))

'frozenset' object has no attribute 'add' <class 'AttributeError'>

for elem in s:
    print(elem)

b
a
c

s1 = {1,2,3}
s2 = {2,3,4,5}

s1 | s2

{1, 2, 3, 4, 5}

s1 & s2

{2, 3}

s1 ^ s2

{1, 4, 5}

Mutability

a = [1,2,3]
b = a

a is b

True

id(a) == id(b)

True

b.append(4)
b

[1, 2, 3, 4]

a

[1, 2, 3, 4]

a = [1,2,3]
b = a[:]

a is b

False

b.append(4)

b

[1, 2, 3, 4]

a

[1, 2, 3]

Nested lists?

a = [1, [2,3,4], 5]
len(a)

3

b = a[:]

b[0] = 666

b

[666, [2, 3, 4], 5]

a

[1, [2, 3, 4], 5]

b[1].append(666)

b

[666, [2, 3, 4, 666], 5]

a

[1, [2, 3, 4, 666], 5]

File I/O

f = open('/etc/passwd')

block = f.read(10)

len(block)

10

block

'root:x:0:0'

f.readline()

':root:/root:/bin/bash\n'

f.readline()

'bin:x:1:1:bin:/bin:/sbin/nologin\n'

f.readline()

'daemon:x:2:2:daemon:/sbin:/sbin/nologin\n'

… und so weiter …

f = open('/etc/passwd')

for line in f:
    print(line.rstrip())   # <--- strip trailing newline

root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
tss:x:59:59:Account used for TPM access:/dev/null:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/usr/sbin/nologin
systemd-oom:x:999:999:systemd Userspace OOM Killer:/:/usr/sbin/nologin
systemd-resolve:x:193:193:systemd Resolver:/:/usr/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
polkitd:x:998:997:User for polkitd:/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
unbound:x:997:995:Unbound DNS resolver:/etc/unbound:/sbin/nologin
nm-openconnect:x:996:994:NetworkManager user for OpenConnect:/:/sbin/nologin
geoclue:x:995:993:User for geoclue:/var/lib/geoclue:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
gluster:x:994:992:GlusterFS daemons:/run/gluster:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
chrony:x:993:990::/var/lib/chrony:/sbin/nologin
saslauth:x:992:76:Saslauthd user:/run/saslauthd:/sbin/nologin
dnsmasq:x:991:989:Dnsmasq DHCP and DNS server:/var/lib/dnsmasq:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
colord:x:990:988:User for colord:/var/lib/colord:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
openvpn:x:989:987:OpenVPN:/etc/openvpn:/sbin/nologin
nm-openvpn:x:988:986:Default user for running openvpn spawned by NetworkManager:/:/sbin/nologin
pipewire:x:987:985:PipeWire System Daemon:/var/run/pipewire:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
flatpak:x:986:983:User for flatpak system helper:/:/sbin/nologin
gdm:x:42:42:GNOME Display Manager:/var/lib/gdm:/sbin/nologin
gnome-initial-setup:x:985:982::/run/gnome-initial-setup/:/sbin/nologin
vboxadd:x:984:1::/var/run/vboxadd:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/usr/share/empty.sshd:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
jfasch:x:1000:1000:Joerg Faschingbauer:/home/jfasch:/bin/bash
systemd-coredump:x:978:978:systemd Core Dumper:/:/usr/sbin/nologin
systemd-timesync:x:977:977:systemd Time Synchronization:/:/usr/sbin/nologin
mosquitto:x:976:976:Mosquitto Broker:/etc/mosquitto:/sbin/nologin

f.close()

def read_lines_of_file(filename):
    f = open('/etc/passwd')
    lines = f.readlines()
    return lines

lines = read_lines_of_file('/etc/passwd')

with open('/etc/passwd') as f:
    # read file
    pass

try:
    f = open('/etc/passwd', 'w')
except Exception as e:
    print(e, type(e))

[Errno 13] Permission denied: '/etc/passwd' <class 'PermissionError'>

enumerate()

l = ['Joerg', 'Faschingbauer', 'blah']

for elem in l:
    print(elem)

Joerg
Faschingbauer
blah

for elem in enumerate(l):
    print(elem)

(0, 'Joerg')
(1, 'Faschingbauer')
(2, 'blah')

for pos, elem in enumerate(l):
    print(f'[{pos}]: {elem}')

[0]: Joerg
[1]: Faschingbauer
[2]: blah

'-'.join(['Joerg', 'Faschingbauer', 'blah'])

'Joerg-Faschingbauer-blah'

class

class Foo:
    pass

f = Foo()

print(type(f))

<class '__main__.Foo'>

f.__dict__

{}

f.bar = 'Blah'

f.__dict__

{'bar': 'Blah'}

f

<__main__.Foo at 0x7f32c7d8d390>

class Foo:
    def __init__(self, bar):
        self.bar = bar

f = Foo('blah')

f.bar

'blah'

f.__dict__['bar']

'blah'